1. Field of Invention
The present invention relates to disposable lighter, and more particularly to a disposable childproof lighter wherein the driving caps are normally disengaged with the gear wheels which drive the striker wheel to ignite, so as to prevent the disposable lighter from being ignited accidentally or by children.
2. Description of Related Arts
Nowadays, both U.S. government and U.S. Consumer Product Safety Commission demand a safety device in every cigarette lighter including the disposable lighter to prevent unwanted ignition accidentally or by a child. As it is known that the disposable lighter is common and relatively cheap, it is impossible to incorporate with expensive and complex safety device that highly increases the cost of the disposable lighter. In order to minimize the manufacturing cost of the disposable lighter employed with safety device, one of the most common disposable safety lighter is the driving wheel type disposable safety lighter. This type of disposable lighter comprises a pair of driving wheels for driving the striker wheel to rotate in order to generate sparks, wherein the driving wheels normally run idle when the driving wheels are physically disengaged with the striker wheel.
For example, U.S. Pat. No. 5,547,370, owned by Hwang, discloses a wheel axle mounted between two upright supports at the top of a butane wheel, two driving wheels mounted around the wheel axle and disposed in contact with a spring-supported flint below and turned by the driving wheels through the wheel axle to strike the spring-supported flint in producing sparks. The wheel axle is made of polygonal cross section, having two round rods at two opposite ends loosely inserted into a respective axle hole on each upright support so as to ensure a better connection between the striker wheel and the wheel axle.
Another example is U.S. Pat. No. 5,997,281, owned by Lei discloses two side thumb-wheel each having a circular shallow indentation are respectively mounted on two sides of a friction thumb-wheel, wherein each circular shallow indentation has an inner diameter slightly larger that an outside diameter of the friction thumb-wheel such that the friction thumb-wheel can be inserted into the circular shallow indentation. In such arrangement, when a pressing force is applied on the two side thumb-wheels, the side thumb-wheels will engage with the friction thumb-wheel, which in turn bears against a flint to create a spark.
However, most of the driving wheel type disposable safety lighters, including the above two patents, still have the following drawbacks.
Since the dimension of the driving wheels (side thumb-wheels) are not produced precisely for minimizing the manufacturing cost of the disposable lighter, there is always a clearance between the driving wheel and the striker wheel. The clearance is supposed to provide a gap that the driving wheels can rotate loosely around the axle in such a manner the driving wheels are run idle around the axle. However, the clearance also provides a gap that the driving wheels can axially loose such that the driving wheels may not perfectly engage with the wheel axle of the striker wheel in order to provide an optimum mutual friction therebetween for ignition. Furthermore, in order to ignite the lighter, a downward force must applied on the driving wheels for engaging the striker wheel. In fact, the driving wheels are always engaged with the wheel axle of the striker wheel by gravity which acts as the downward force. In other words, the lighter, which claims as a safety lighter, may normally in a ready-to-ignite position.